[SEL] Piston slap ????

[Graham Harris]

Gday Tom

I've noticed a similiar problem on my Sundial 4HP, an Oz built horizontal engine, closed crankcase, 5" bore, thrott gov. All bearings tight (i.e. good) and no slop in a good bore, and fresh rings. As it coasts to a stop (use the magneto stop button) I get a audible knock from the crankcase at < 100RPM till it stops and a small fore-aft rocking. The knock is not coming from anywhere on the transporter.

Interested to hear suggestions you get, wondering maybe if being a throttle governed engine, and the butterfly almost closed, the (very good) compression could be doing it? Sounds just like a loose big end or gudgeon, but not in my case. It is really weird. What make is your engine?


Graham in Oz



Got a question for you guys.  I'm working on an engine and it has a knock in it and you only hear it when the engine is coasting down really slow but the slower it gets the louder it gets.  The noise is coming from the cylinder and it has been sleeved so that rules out egg shaped cylinder.  Only thing that I can come up with is piston slap but I've taken a piston and rod out of an identical engine here and it does the same thing but the other engine doesn't make the noise and it's pretty irritating noise and is pretty loud.  You can't hear any loud knocking when the engine is running at a decent speed but only when slowed down to under 100 rpm that the noise starts.  Any ideas or suggestions are appreciated

Thanks
Tom Winland
Ohio



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